Route-finding device



p 2, 1952 R. F. HANSFORD 2,608,770

ROUTE-FINDING DEVICE I Fil ed Feb. 25, 1948 2 sums-sum 1 INVENTOR REGINA/.0 EHHNSFORD R. F. HANSFORD ROUTE-FINDING DEVICE Sept. 2, 1952 Filed Feb. 25, 1948' lNVE NTOR REGINALD EI /H/VSFORL MX ms ATTORNEY Patented Sept. 2, 1952 .v oUTiiFiunmG DEVIC v ReginaldFrederickflansford, Bognor Regis, L

land, assignor t o'The Sperry Corporation, Great Neck, Ya, a corporation of Delaware I I Application February 25, 1948, Serial No. 1 0,901

3 in Great Britain November 29,1946

"season- 1-,- Public Law ssmnuguses, .1946 V Patent expires November 29, 1966- This invention relates to. devicesz foifdfindinlg f and indicating the shortest route; between any twop'ointsi among a number that "are :i'ntercon; ne'ctediby 'a maze of paths. It will-be understood that the terms points? and (paths-are used,- in,

a very general manner-and.the.iterm,ashort "is also-used in a generalised manner; to embrace noeonly short .in a "geometrical senseiasa meas ureofidistahce; but also to embrace thejmeasure merit of such matter' e as the 1 time required .to;

travel between any of the points. zalongaacertain;

r oute' and theitotal resistance to the '-flowof;a

fluid'or' ofLelectricityalongacertain route; 1 According to the present invention a-gqroute fir'idlinev device comprises. a ;mazeco'f channels inter'c zo'nnecting'"a plurality of points-and having? incorporatediin, or coupled by; means of an im; pedanc'e-transforming; device .01 devices-winto, each "channel; one .or. more ,threshold devices, means for connecting to the-maze atone of the points'and at any selected; other of the points agent-tends pijef erentially iQfiO or o rat in'the sh0rtest routebetweent e wo oints,- that is :in thati'iioutebetween the twopointsffj or which thetotal; effective threshold value -i the lowest The flow or operation of the workine a ge 1': this shortest route qausesea degradation, fdissipa tion'mor; absorption of some of the pressure or forcemf; the, working agent in the throttling' i means-,-;s0.that the resultant v -pressu're. or force; difierencerbetween the two :point is 1 lower, than any greater-total threshold values of vother routes that may exist-.betweenthe two points. Consequently;theyworleingagent will i 1 v through or operate substantially exclusively in the route be: tween the two points that has the. smallest total effective threshold value. I-h e threshold devices furthermoreare preferably of sucha nature that,

input and output channels:foraworking agent}; and throttling means" in the input or,output;

channel or in both.- v.;, v. H -The term' -thr'eshold device is;herein used to mean a devic ethat prevents forge-ready impedes the flower operation. of the working agent when; the pressure or .forcet'o which the threshold; device is subjected by the working 'agent isbelowa certain threshold value; but impedes the;- flow or operation: of the working ga gent substantiallythe threshold having beenexceeded andfio'w or operation of the working agent having been initiated -such flow or-pperaticihjis permitted to continue relativelyunimpeded until the pressure or force to which the-threshold device is subject becomes appreciablylower than the threshold less,-onlygalittle- 01' not;;-at all; whenthe press ire;

oriforce to which. it is: subjected byg'th verging:

agent'isgreater than thethreshold velue 'lfhe term .throttling meansi, is used to-embrace any;

means that, inv lpermittingjhe flow or operation of the working agent-degrades; dissipates \or absorbssome portion of the pressure-{enforce ofthe working agent. For ex -ample gin thecase oi a fluid working agent the throttling ;:means may be ra constricted conduit or in; the; case ofi'elec tricity it maybe an impedance, such as a resist-- ance for continuous-current electricityor a reactance forelternating-eurrentelectricity; I

v thee-operation of the, device, thetotal -value of the pressure or force of the -v: zorl :ir 1g agent that must be app ied. t i 'a ifil d n f an 2 ne by coupli ii'g into its ehannelsi Tl-ie working value of; the pressure or'force atiwhich the flow ori,.;operation;wa s initiated, If then there be a plurality of -routes all having-identicaltotal efrec tive thresholdgvalues lower thanthat' of any v lar route ,ofthe plurality H orking agentfl0wsor bperates' is determined"; at; random. -l-lo weve'r', if desired; in any' -case whioh a pluralityof routes are nor; mallysofiegual zleneth and it is desired that one of these should be preferentiallyadopted, the thresholdlwfievi'cesof that. onev route, or the H v iceswjincludedl in, any. particular channel that' route, .mayZbegivenjailower' h-re'shold devices in alternathreshold than tiyemoutes of ithe p l-urality. v v,

l parrying: out-othe'finvention vthe threshold devices: maybe any devices such. that the remtionsh'ip -betweer -r applied pressure or .force' and the: permitted now orpperation oi the working; agent-:1 not one ,of, -mutua 1- proportionality and piffifflhlY; WhQIQ ShLOWIL- the f orm of a graph, has an abruptlmee or bend. If this knee or bend occurs atfa value; of pressure or force diit'ererit from the desired threshold value. for any particulareth'r'eshold dev-ice,- anaux'iliary source of biasfo'ree dri pressureilmay: be associated :with that threshold device' to bring the workingythreshold of the"- combination-to the required value of ap plied pressure or force-z; -v i In icarryiiig ioutetheinvention practice.- the working agent-may heaqfluid und pressure in which .Icase :the: channe1 s: interconnecting the cator. The working agent, a gas or liquid, may i be supplied or circulated under pressure by any suitable form of pump.

It is preferred, however, to carry out the inven-' tion electrically, in which case the channels comprise electrical conductors and the threshold devices consist of any of a number of well known devices having a relation between impressed voltage and resultant current flow that is other than one of mutual proportionality, such as thermionic valve rectifiers or hot or cold cathode gas or vapor discharge tubes, if necessary combined each with a source of bias electromotive force to bring its effective threshold to the required value. In such case the throttling means comprises an electrical impedance, a resistance in thecase of continuous current supply.

The invention is particularly applicable to finding and indicating the shortest available route from point to point upon telecommunication networks, railway systems, tramways systems and other communication systems involving mazelike networks. For the better understanding of the invention a railway route indicator incorporating it will nowbe described by way of example only with reference to the accompanying drawings. in which:

Fig. l is a typical part cross section of a preferred form of route indicating device in accordance with the invention;

Fig. 2 is a schematic electrical diagram demonstrating the electrical circuits of a route indicating device in accordance with the invention;

Fig. 3 is an electrical circuit diagram showing a modification applied to two typical channels in which the threshold devices, instead of being directly incorporated in the channels of the maze, are coupled. by means of impedance transforming devices into each channel; and

Fig. 4 is a circuit diagram showing a modification of. part of the electrical circuits demonstrated in Fig. 2 for 'the purpose ofsupplying power to the maze by 'means of continuous electric current instead of alternating electric current.

Like reference numerals are utilised to indicate like parts, where applicable, throughout the several figures of the accompanying drawings- As shown in Fig. 1 the railway route indicator comprises a flat base 10,} preferably of electrically insulating material, over which is mounted a cover ll of transparent or translucent material, such as glass. An opaque sheet [2, of paper, card or even paint is arranged beneath the cover I l and upon it is presented a display representing the whole railway network together with the points of interchange. Elongated openings or slots 13 are provided in the opaque sheet I2 in positions corresponding with the various branches of the railway network as displayed upon the sheet 12. Beneath the sheet I2 is arranged an electrical network, diagrammatically illustrated in Fig. 2 having neon glow lamps i5 disposed beneath the various openings or slots [3 so that they may be observed-.throughthe cover H, and also beneath therepresentations of the various points of interchange on theraili inclusive.

way network. These glow lamps iii are preferably of elongated tubular form, as shown, and may be mounted by means of electrically conducting brackets l4 upon the base 10, if the latter is of electrically insulating material. The glow lamps 15 are preferably without ballast resistances, so that, once their ignition voltage is exceeded, the voltage across their terminals is sub stantially independent of the current that flows through them. Such glow lamps also have the property that their extinction voltage is lower than their ignition voltage.

Referring now to Fig. 2 which shows an electrical maze of channels interconnecting points z and a to o inclusive corresponding respectively to stations of entrance and interchange of a particular railway network, the number of lamps l5 included in each channel of the electrical network is, as near as is practicable proportional to the average time of transit through the corresponding branch of the railway system. Thus there are, for example, two lamps I5 in the channel connecting the points I and m representing two units of transit time; and between the points b and i there are three lamps, representing three The particular electrical maze shown in Fig. 2

is arranged for indication of the shortest route between the point z and any of the points a to 0 Thus the point z of the electrical maze is connected to one terminal of a source of high voltage alternating electrical supply, typified by the secondary winding. 16 of a stepup transformer 11, whose primary 18 may be.

connected to alternating electric mains. The several points a t o inclusive of the electrical maze are respectively connected to corresponding contacts of pressel or similar selector switches A to O inclusive. The remaining contacts of these selector switches A to O inclusive are all connected together and through throttling means inv the form of a resistance l9 to the remaining terminal of the secondary winding l5 of the transformer H. 7 I

If it is desired, not onlyto obtain indication of the shortest route between the point on the railway network represented by. the points of the electrical'maze and any other point of the railway network represented by one of the points a to o inclusive of the electrical maze, but also to obtain 'an approximate indication of the average time required for transit over this route, a high-resistance voltmeter 20 may be connected,

as shown in Fig. 2 between the junction of the resistance I9 with the'common point of switches A to O inclusive and the point 2 so that this voltmeter indicates the voltage developed at any time across the electricalmaze alone and-excludes the voltage drop in the resistance l9. For this purpose, alternatively a milliammeter may be connected in series with the secondary winding it, or a suitable ammeter may be connected in series with the primarywinding 18, but such an arrangement has a lower degree of accuracy. In a practical case the lamps l5 may be small tubular neon filled discharge lamps having an ignition voltage of about 200 volts; an extinction voltage of about voltsi'and operatingsafely with "a current .ofLa'bou't; l milliampera The transformer l1 shouldthenbe such that the; peak voltage somewhat exceedszoii inultipl-ied by the number ofiampsinvolved in representation" of the-shortest route betweenthe two most distantpoints of the railway network Quite highjvoltage may therefore be needed. Consequently "the selector switches A- to Q inclusive: should be such as adequately andsafely to control the necessary high voltage. i

When alternating electric supply is used, as shownin-Fig. 2, the resistance: I 9 may, if alesired; be substituted by-achoke-coil or condenser, that, having: regard' to the frequency of the -sup--- ply, produces an adequate 'voltage'drop: when current flows-through it. I t I In the operation of the device shownin Fig. '2 ifit' be. desired that theshortest' route "between the point of the-railway net-work-corresponding to; thepointzof the electrical "maze: and anyother point on the network, theone of the selector switches A to. O inclusive, that-pertains to the corresponding point on the electrical maze is closed manually. As the alternating; voltage applied risesfrom zero in any half cycle, it. reaches a value equal'to the sum of the threshold ori'gni tion voltages-of the lamps included inthe-short est route (minimum -n um'be'r of lamps) interconnectingthe point z with the point cf tlie maze corresponding to which a selector switch hasbeen closed. Current-then-commences-to flow through that routeandthe lamps comprised in it are illuminated. Further increase of the voltage of the transformer secondary 'windi ng it tends to-caus'e more. current to flow through the lamps thatare already ignited, the voltage applied-to the maze being maintained constant or nearly so at a value somewhat below thatzinitially required to ignite the lamps. The excess voltage induced in thetransformer secondary I 6 is "dissipated in the throttling resistance It. Consequently a voltage sufficiently great to ignite the lamps of a routebetween the two points con'rip'rising' more neon lamps than those already ignited cannot be applied to the electrical mazeand therefore the lamps. of the shortest route. only are ignited. These ignited lamps are extinguished in themaze' for the one-half cycle of thea'lternating' supply, and are re-ignitedduring" the waxing of the next subsequent halfcyclc. so long: as: the appropriate switch is. pressed.

Since the voltmeter 2111 isconnected across the maze only, its reading depends upon the number of lamps in series that are ignited in the shortest route through the maze from the point a to the actuated switch. Its reading may therefore be considered as a measure of the distance and therefore transit time by the shortest route through the railway network from the point represented by the point z of the electrical maze to the point of the railway network corresponding to the switch that has been actuated.

As has been explained, a high voltage is needed for operation of the arrangement shown in Fig. 2. The arrangement shown for two routes only in Fig. 3 may be employed to reduce the necessary peak voltage when an alternating electrical supply is used, and this arrangement also has other advantages.

As shown in Fig. 3, in one channel of the electrical maze, controlled by the switch A, two glow lamps l5 are individually coupled into the channels by means of impedance transforming devices that in this case take the form of electrical transformers 22 and 23. These transformers may have voltage transformation ratios of any suitable value so that the voltage developed in pointcorresponding. to win 6 theiri primary windings is-a fractihn of that veloped across-their respective lamps I Morel-e over the various transformers; such as Elan-dill may have. different; voltagetransformationiratins so that lamps having similar characteristicsmayi be used'to represent; different. transiti'times.

It in: such. an. arrangement as isshcwn 2: there: be between the: pointzaandi anyother two; or more; routes through the; electrical' mazecomprising equal numbers of. lamps; which there routes-will be illuminated. inqresponse closure; of: any particular switch. is; a. matterqot pure chance, .unlesssom'e formof bias ina'fiavourtoa against a particularxroute: onroutesis introduced; Such. a bias maybe introduced into; any'ichanneli of the mazershown; inFigz. Z by' includiirig m it channel. the-secondary winding; developin a moderateyor low; voltage. of; a transiiormer of? whichthe-nrimaryr is connected. witlrqthetalten hating source orisupply. fror examnlermraralleii with they primary-winding; It, ufsthe transfonnar. it. A similarbiassing; arrangement is shown-in i i ln the. channel shown in Fig.- that= ,i s= trolled by the switch 13! thre clamps I55; coupledrespectively bytransformers 24, 2 5. 26 into the channel. The secondary windingli. of a biassing transformer 2-8 is hozweverconncctcd in series. with the secondary:- winding; of the trans;-T former 26; andits lamp; 'Ifhe: primary wig of the transformer 281s. connectedwiththe I of lternating.electricsupply. If thetransfo 2-8 be so connectedthat. the; electromotiv mm. ofits secondary winding is energized. ondary windingof thetransformer 2d,;ign1 0 the lamps associated 'withthischannel:will ak place. preferentially. and. only the mute prising this channel will be illuminated..-,

,When. an alternating supply I isutili'zed, as scribed with reference to Figs. 2am! 3 transient effects sometimes. occur. that resultrm par li illuminationor flickering. ofthe lampsassocia withthe channel's. notiincl'udedin. the shor 1;

route between the. point a of the. maze. and; I a switch has. been closed." Itislftherefore. stem-red: inImost t'o. employfcontinuous current.for cnerg z' of. a; route-iiidi'ating, dYvic;v empliying'neon glowlamps'... v T I To. this, endltha'point. z: and. the. 'end ofthe sista'nc'e l9 may be connectedto a source of'high voltage continuous current. However, where an alternating supply is available, a rectifying diode 29 may be connected, as shown in Fig. 4, with the secondary winding [6 of the transformer H. The cathode of this diode 29 may be heated by connection with an additional secondary winding 30 of the transformer I! in a conventional manner. The rectified output of the diode may be smoothed before application to the resistance by means of an additional series impedance 3| and shunt capacity 32.

It will be appreciated that certain specific forms of electrical route finding devices have been described with reference to and shown in the accompanying drawings by way of example only, and that many modifications may be made,

without departing from the scope of the invenaplurality of routes between a plurality of pairs of-points, an energy source-and means for connecting said source simultaneously to apply energy to: all of said channels which represent routes between the two' desired points, a plurality of gas discharge tubes connected in each of said channels, the number thereof in any one channel depending upon the length of the route represe'ntedby that channel, said gas discharge tubes being operable to impede the how of energy therethrough when the energy level is below a predetermined value but to freely conduct energy therethrough when the energy level is equal to-orabove said predetermined value, whereby energy suflicient to operate the gas discharge tubes'will flow only through that channel comprised in said plurality of channels having the leastnumber of tubes included therein to theexclusion ofany of the remaining channels havi'ng a greater number of tubes included therein, and a'meter connected in circuit with said energy source and all of said channels for indicating the magnitude of the energy consumed in the respective channels whereby the approximate travel time required to traverse the route corresponding to an energized channel may be indicatd.

2. A route finding device comprising, a maze of electrically interconnected channels representing routes between a plurality of pointsand a plurality of routes between a plurality of pairs of points, asource of electrical energy having one side thereof connected to a point in said maze representing present position, a plurality of switches connected to a plurality of points representingdestination positions and connected to the other side of said source whereby actuation of a selected one of said switches applies energy to all channels which may exist between the point representing present position and the point representing the destination position, and a plurality of gas discharge tubes in each of said channels, the number thereof in any one channel depending upon the-length of the route represented by that channel, said tubes being operable to shunt energy therethrough only when energy of a: suflicient magnitude is applied thereto to cause the tubes in the desired path to discharge whereupon the operation of the tubes, in any other of the energized channels is thereafter prevented.

3. A device of the character set forth in claim 2 in which a pair of the channels representing routes between two points each has substantially the same number of gas discharge tubes included therein, andrbias means coupled with one of said.

pair of channels for altering the energy level at which the tubes included in that one channel will operate.

4. In a device for determining the shortest route from one point to a selected point among a plurality of routes between said points, a maze of electrically interconnected channels representing routes between a plurality of points and a plurality of routes between a plurality of pairs of points, an energy source and means for connecting said source simultaneously to apply energy to all of said channels which represent routes between the two desired points, a plurality of gas discharge tubes connected in each of said channels, the number thereof in any one channel depending upon the length of the route repre-v sented by that channel, said gas discharge tubes being operable to impede the flow of energy therethrough when the energy level is below a predetermined value but to freely conduct energy therethrough when the energy level. is equal to or above said predetermined value, whereby energy sufficient to operate the gas discharge tubes will flow only through that channel comprised in said plurality of channels having the least number of tubes included therein to the exclusion of any of the remaining channels having a greater number of tubes included therein, andmeans for indicating the magnitude of the energy consumed in the respective channels whereby the approximate travel time required to traverse said one channel may be indicated.

REGINALD FREDERICK HANSFORD.

REFERENCES CITED The following references are of record in the file of'this patent:

UNITED STATES PATENTS 

